The invention relates generally to the control of multiple storage devices, such as disk arrays.
Storage systems have grown enormously in both size and sophistication in recent years. These systems can typically include many large disk drive units controlled by a complex, multi-tasking, disk drive controller such as the EMC Symmetrix disk drive controller. A large scale disk drive system can typically receive commands, such as I/O requests, from a number of host computers and can control a number of disk drive mass storage devices, each mass storage device capable of storing in excess of several gigabits of data.
There is every reason to expect that both the sophistication and the size of the disk drive systems will continue to increase. As the systems increase in complexity, so does a user's reliance upon the system for fast and reliable recovery and storage of data. Accordingly, the user typically uses data throughput and speed of response as a primary criteria for evaluating performance of the disk drive systems. As a result, mass storage devices and the controllers which drive them have become quite sophisticated in trying to improve command response time. Systems such as the EMC Symmetrix disk drive controller system thus incorporate a large cache memory, and other techniques to improve the system throughput.
Of course, with the increase in size and complexity of such disk drive systems, comes a tremendous increase in the number of command requests making monitoring of the performance of the systems more difficult.